The invention relates to a washing machine or a washer-dryer having a plastic liquor container, essentially consisting of two plastic components. In the following reference is only made to washing machines without hereby wishing to restrict the application of the invention also to washer-dryers.
The invention is suitable in particular for use with front-loading washing machines. Such washing machines, known as front loaders, are characterized in that the laundry drum that can rotate in the liquor container has an essentially horizontal orientation and is supported on one side by way of a rotating pin. To support the rotating pin, the rear wall of the liquor container has a bearing receptacle disposed in its center. The rotating pin is connected to a motor directly or by way of a pulley, said motor driving the laundry drum from the outside.
The fact that the drum is supported on one side means that the requirements relating to mechanical strength are particularly stringent in the abovementioned front loaders. Very high rotational and bending forces occur in particular during spinning as a function of the speed of the laundry drum and the loading of the drum. The forces transmitted in the process from the laundry drum, which is supported on one side, by way of the bearing receptacle of the rotating pin to the liquor container subject the rear wall in the region of the bearing receptacle to the greatest stress. The attacking forces have to be absorbed by the bearing receptacle and transmitted or distributed to a significant extent to the outer regions of the rear wall.
The liquor container has to be structurally designed so that all the regions of the rear wall have an adequate mechanical strength in respect of the specific stresses. Since the mechanical strain on the rear wall of the liquor container is at its greatest in the region of the bearing receptacle and decreases from the bearing receptacle by way of the end side wall toward the container jacket, from the point of view of economical production of the liquor container, it must be ensured that the individual regions of the liquor container rear wall are not excessively dimensioned. Material usage should be kept to what is functionally necessary for each liquor container.
In addition to liquor containers, the rear wall of which is reinforced by means of a metal bearing bracket (e.g. EP 1 528 136 A2), liquor containers in which a high-strength plastic are used to reinforce the rear walls are also known from the prior art.
The technology for producing the liquor container is standardized by dispensing with a metal bearing bracket. It is possible to reduce technical and organizational production outlay as well as economic production outlay considerably. It is also possible to avoid the risks that arise with a liquor container with a metal bearing bracket that materials are used that have very different physical characteristics. The different expansion coefficients and thermal conductivities of the metal and plastic mean that after injection has taken place around the bearing bracket in the liquor container rear wall, considerable tensions can occur, which can result in cracks in the plastic.
WO 2004/042133 should be mentioned as an example of a liquor container produced using two different plastic components. The liquor container described therein has a metal bearing dish with a body made of a strong, high-quality plastic. The plastic is injected according to known methods. The metal bearing dish and the plastic body form a structural unit. In a following method step the liquor container jacket is injected on. A less strong plastic that is much cheaper is used for the container jacket.
The disadvantage of the structure is that the stabilizing effect of the additional body with the strong plastic is restricted to the region of the bearing receptacle. The strong plastic has no or little effect on the stability of the rear wall of the liquor container.
Plastic liquor containers are also known, in which an additional stabilizing component is used to stabilize the end side wall from the outside, being made of a stronger and better quality plastic than that of the liquor container jacket. The stabilizing component and the end side wall of the liquor container are injection molded parts, which are welded together. Reinforcing ribs are molded into the known stabilizing component and/or into the end side wall, said ribs being shaped to correspond to one another, so that the backs of the reinforcing ribs adjoin the opposing surface along their extension without any gaps.
The last described liquor container is characterized by a high level of strength. The number of molded in reinforcing ribs and their different dimensions, as well as the option of electing to mold reinforcing ribs into the stabilizing component or end side wall mean that with effective material deployment liquor containers can be produced the strength of which is based on the specific stresses during operation of the washing machine.
The disadvantage of the last described liquor container is that the parts produced by injection molding have to be joined together in a subsequent process, with the parts being positioned against one another in a first method step and then being welded. The welding methods are known and are easily mastered. Manufacture of the liquor container therefore has the major disadvantage that in addition to injection molding a second technology has to be employed, which requires additional equipment.